Among thin-type image display devices, a plasma display panel (hereinafter simply referred to as “panel”) allows high-speed display and can be easily upsized. Thus a plasma display panel is commercialized as a large-screen image display device.
The panel is formed of a front plate and a back plate bonded together.
The front plate has the following elements:
a glass substrate;
display electrode pairs, each formed of a scan electrode and a sustain electrode, disposed on the glass substrate;
a dielectric layer formed to cover the display electrode pairs; and
a protective layer formed on the dielectric layer.
The protective layer is disposed to protect the dielectric layer from ion collision and to facilitate generation of discharge.
The back plate has the following elements:
a glass substrate;
data electrodes formed on the glass substrate;
a dielectric layer covering the data electrodes;
barrier ribs formed on the dielectric layer; and
phosphor layers formed between the barrier ribs and emitting light of red, green, and blue colors.
The front plate and the back plate are faced to each other so that the display electrode pairs and the data electrodes intersect with each other and sandwich a discharge space between the electrodes. The peripheries of the plates are sealed with a low-melting glass. A discharge gas containing xenon is sealed into the discharge space. Discharge cells are formed in parts where the display electrode pairs are faced to the data electrodes.
In a plasma display device having a panel structured as above, a gas discharge is caused selectively in the respective discharge cells of the panel, and the ultraviolet light generated at this time excites the red, green, and blue phosphors so that light is emitted for color display.
A subfield method is typically used as a method for driving the panel. That is, one field period is divided into a plurality of subfields, and gradation display is provided by the combination of subfields in which light is emitted. Each subfield has an initializing period, an address period, and a sustain period. In the initializing period, predetermined voltages are applied to the scan electrodes and sustain electrodes, to cause an initializing discharge and to form wall charge necessary for the subsequent address operation on the respective electrodes. In the address period, a scan pulse is sequentially applied to the scan electrodes, and an address pulse is applied selectively to the data electrodes to cause an address discharge and form wall charge. In the sustain period, sustain pulses are applied alternately to the display electrode pairs. Thereby, a sustain discharge is caused selectively in the discharge cells to cause the phosphor layers of the corresponding discharge cells to emit light. In this manner, an image is displayed.
In order to display a high quality image, control is made so that the discharge cells to be lit are lit and the discharge cells to be unlit are unlit without fail. For this control, it is necessary to perform reliable address operation within an assigned time period. For this purpose, development of a panel that can be driven at high speed is promoted, and studies are proceeding on a driving method and a driving circuit for displaying high quality images by making full use of the performance of the panel.
The discharge characteristics of a panel depend largely on the characteristics of its protective layer. Particularly, in order to improve electron emission performance and charge retention performance that have considerable influence on whether or not the panel can be driven at high speed, many studies are made on the materials, structures, and manufacturing methods of the protective layer. For example, Patent Literature 1 discloses a plasma display device that has a panel and an electrode driving circuit. In this plasma display device, the panel includes a magnesium oxide layer that is made from magnesium vapor by gas-phase oxidation and has a cathode luminescence light emission peak at 200 nm to 300 nm. In address periods, the electrode driving circuit sequentially applies a scan pulse to one electrode of each one of display electrode pairs constituting the all display lines, and supplies, to the data electrodes, an address pulse corresponding to the display lines applied with the scan pulse.
In recent years, a plasma display device having high definition as well as a large screen has been demanded. For example, a high-definition plasma display device that has 1920 pixels×1080 lines, and an extremely high-definition plasma display device that has 2160 lines or 4320 lines have been demanded. While the number of lines is increased as described above, the number of subfields for displaying smooth gradation needs to be secured. Thus the time assigned for the address operation per line tends to be further shortened. Therefore, in order to perform a reliable address operation within the assigned time, there is a demand for a panel capable of performing more stable address operation at higher speed than those of conventional arts, a driving method for the panel, and a plasma display device that has a driving circuit for implementing the method.
[Patent Literature 1] Japanese Patent Unexamined Publication No. 2006-54158